There are growing evidences suggesting a pivotal role of oxidative stress in the pathophysiology of preeclampsia. We investigated oxidative stress in the rat model of preeclampsia, and in clinical cases. Pregnant female rats were injected intraperitoneally with deoxycorticosterone acetate (DOCA) and given 0.9% saline as drinking water during their pregnancy. We assessed plasma F2-isoprostane (8-iso-PGF2α) and malondialdehyde (MDA) in a rat model, and the same markers in the plasma of maternal blood and fetal cord blood in pregnant women with preclampsia. Blood samples from the umbilical arteries and veins were collected separately. The concentrations of MDA were increased in the preeclampsia groups of animal and humans, compared with the control group; it was significantly increased in the umbilical artery and vein of the preeclampsia group. The concentrations of F2-isoprostane were elevated in the preeclampsia groups of animal and humans, compared with the control group, and the increase in F2-isoprostane concentration was prominent in the umbilical vein than umbilical artery of the preeclampsia group. Therefore, it appears that the placenta has an important role in the pathophysiology of preeclampsia, and the F2-isoprostanes of the umbilical vein may serve as a relatively reliable marker for ischemic/hypoxic injury to the fetus during the perinatal period.